WO-A1-2004/072449, the disclosure of which is incorporated herein in its entirety, describes an automotive air blower in the form of a supercharger for use with an automotive engine. The supercharger differs from a conventional supercharger in being operable to augment rotary power from the engine crankshaft with rotary power from one or more electric motors housed in a body of the supercharger.
More specifically, the supercharger includes an input shaft for coupling by a transmission belt to the crankshaft of the engine, and also includes an output shaft to which is fitted an air impellor. The supercharger further includes an epicyclic gear train, and first and second motor-generator electrical machines. The arrangement is such that the input shaft is coupled to the annulus of the epicyclic gear train and to the rotor of one of the electrical machines; the output shaft is coupled to the sun wheel of the epicyclic gear train; and the carrier of the epicyclic gear train is coupled to the other electrical machine.
This supercharger is advantageous in that it is operable to vary the pressure of air in the inlet manifold of the engine independently of the engine speed, and in an efficient and cost-effective manner. By varying the air pressure independently of engine speed, the supercharger can be very responsive to changes in load.
An object of this invention is to provide a method of operating superchargers similar to that described above.
At present, some drivers of passenger vehicles, such as cars (or “automobiles” in American English), favour larger engines over smaller engines. This is because larger engines offer certain performance advantages over smaller engines in terms of greater power output and, in the case of larger engines that have many cylinders, lower levels of noise and vibration harshness (NVH). Larger engines are, however, less efficient to operate and more expensive to manufacture than smaller engines.
Another object of this invention is therefore to provide a method that can be used to provide at least some of the performance advantages associated with a larger engine, and at least some of the cost and efficiency advantages associated with a smaller engine.